The present invention relates to a unidirectional fluid valve that can be used as an exhalation valve for a respirator. In addition the invention includes a respirator that employs such an exhalation valve.
Exhalation valves have been used as part of respirators for many years and have been disclosed in a variety of prior art patents. Two particular prior art patents which disclose a particular type of valve, known as a flap valve, are U.S. Pat. No. 4,934,362 and U.S. Pat. No. 5,325,892. Both of these patents disclose unidirectional exhalation valves that have a flexible flap secured to a valve seat and with the valve seat having a particular profile.
In particular the U.S. Pat. No. 4,934,362 patent has a parabolic profile for the valve seat and the U.S. Pat. No. 5,325,892 patent has a concave curvature for the valve seat corresponding to a deformation curve exhibited by a particular force directed to the flexible flap. Both of the above prior art patents thereby provide for a complex shape for the valve seat. These patents describe a structure to provide for a significantly lower pressure drop so that the free end of the flexible flap may be easily displaced from the valve seat to make the respirator mask more comfortable to wear.